Novel {60 ,{60 {40 -bis(aminobenzylidene) aryldiacetonitrile photoconductors

ABSTRACT

Alpha , Alpha &#39;&#39;-BIS(AMINOBENZYLIDENE)ARYLIDACETONITRILES ARE USEFUL AS ORGANIC PHOTOCONDUCTORS IN ELECTROPHOTOGRAPHIC ELEMENTS. Elements containing these materials exhibit improved speeds.

o lJmted Mates Patent [151 3,653,887

Merrilli Apr. 4, 1972 [5 NUVEL 6!,01'-BIS(AMINOBENZYLIDENE) [56]References Cited UNITED STATES PATENTS 3,246,983 4/1966 SUS et al ..96/l.5

72 I t I St I'II'LM '1] R h t ,N.Y. 1 or ewa em es er FOREIGN PATENTS ORAPPLICATIONS [73] Assignee: Eastman Kodak Company, Rochester,

NY 39/11546 6/1964 Japan ..96/l.5

[22] Filed: 1969 Primary Examiner-Charles E. Van Horn [2]] Appl. No.:874,016 Attorney-Eastman Kodak Company, William H. J. Kline,

James R. Frederick and Fred L. Denson [52] U.S.Cl. ..96/1 PC96/1.5,96/1.6 51 rm. (:1. ..G03g 5/06 [57] ABSTRACT Field ofSearch11,0:-bis(aminobenzylidene)arylidacetonitriles are useful as organicphotoconductors in electrophotographic elements. Elements containingthese materials exhibit improved speeds.

6 Claims, No Drawings NOVEL a,a-BIS(AMINOBENZYLIDENE) ARYLDIACETONITRILEPHOTOCONDUCTORS This invention relates to electrophotography, and inparticular to photoconductive compositions and elements.

The process of xerography, as disclosed by Carlson in US. Pat. No.2,297,691, employs an electrophotographic element comprising a supportmaterial bearing a coating of a normally insulating material whoseelectrical resistance varies with the amount of incident electromagneticradiation it receives during an imagewise exposure. The element,commonly termed a photoconductive element, is first given a uniformsurface charge, generally in the dark after a suitable period of darkadaptation. It is then exposed to a pattern of actinic radiation whichhas the effect of differentially reducing the potential of this surfacecharge in accordance with the relative energy contained in various partsof the radiation pattern. The differential surface charge orelectrostatic latent image remaining on the electrophotographic elementis then made visible by contacting the surface with a suitableelectroscopic marking material. Such marking material or toner, whethercontained in an insulating liquid or on a dry carrier, can be depositedon the exposed surface in accordance with either the charge pattern ordischarge pattern as desired. Deposited marking material can then beeither permanently fixed to the surface of the sensitive element byknown means such as heat, pressure, solvent vapor, or the like, ortransferred to a second element to which it can similarly be fixed.Likewise, the electrostatic charge pattern can be transferred to asecond element and developed there.

Various photoconductive insulating materials have been employed in themanufacture of electrophotographic elements. For example, vapors ofselenium and vapors of selenium alloys deposited on a suitable supportand particles of photoconductive zinc oxide held in a resinous,film-forming binder have found wide application in the present-daydocument copying applications.

Since the introduction of electrophotography, a great many organiccompounds have also been screened for their photoconductive properties.As a result, a very large number of organic compounds have been known topossess some degree of photoconductivity. Many organic compounds haverevealed a useful level of photoconduction and have been incorporatedinto photoconductive compositions. Typical of these organicphotoconductors are the triphenylamines and the triarylmethane leucobases. Optically clear photoconductor-containing elements havingdesirable electrophotographic properties can be especially useful inelectrophotography. Such electrophotographic elements can be exposedthrough a transparent base if desired, thereby providing unusualflexibility in equipment design. Such compositions, when coated as afilm or layer on a suitable support, also yield an element which isreusable; that is, it can be used to form subsequent images afterresidual toner from prior images has been removed by transfer and/orcleaning. Thus far, the selection of various compounds for incorporationinto photoconductive compositions to form electrophotographic layers hasproceeded on a compound-by-compound basis. Nothing as yet has beendiscovered from the large number of different photoconductive substancestested which permits effective prediction, and therefore selection ofthe particular compounds exhibiting the desired electrophotographicproperties.

It is, therefore, an object of this invention to provide a novel classof photoconductors having high photosensitivity when electricallycharged.

It is another object to provide novel photoconductor-containingcompositions which exhibit high electrical speeds.

It is a further object of the invention to provide an improved processutilizing the novel photoconductors described herein.

These and other objects are accomplished by employing a,a-bis(aminobenzylidene )aryldiacetonitriles as photoconductors. Thesematerials can be substituted in various positions by any one or more ofseveral substituents. Typically, the arylene nuclei can be substitutedwith alkyl, aryl, halogen, alkoxy or aryloxy groups while the aminomoiety can have alkyl or aryl substituents. Also, the methyl carbons ofthe benzylidene moieties can be substituted by aryl or alkyl groups.

Various closely related materials having the grouping wherein Ar is anaryl group and R is hydrogen or an active hydrogen-containing group,have been used as photoconductors in electrophotographic systems.Typical materials are set forth in US. Pat. No. 3,246,983 and US. Ser.No. 706,800 filed Feb. 20, 1968 by Brantly et a1 now US. Pat. No.3,567,450. According to this invention, it has been found that thephotoconductors described herein have enhanced speed over thosephotoconductors described in the prior art. In particular, substantialincreases in speeds are obtained as compared to speeds attainable withmany other closely related compounds. These increases in speed areobserved when the coating accepts a suitable potential (e.g., 500-600volts) and the relative speed of the coating is determined on the basisof the reciprocal of the exposure required to reduce the potential ofthe surface charge by 100 volts (shoulder speed) or to 100 volts (toespeed). The terms shoulder speed and toe speed are terms known in thephotographic art with reference to H and D curves. As used herein, suchterms refer to corresponding curves resulting from exposure plottedagainst voltage. The reduction of the surface potential to 100 volts orbelow is significant in that it represents a requirement for suitablebroad area development of an electrostatic image. The relative speed at100 volts is a measure of the ability to produce and hence to develop orotherwise utilize the electrostatic image. When many conventionalphotoconductors are used, the surface potential frequently does not dropto or below 100 volts and therefore no speed can be assigned to such acomposition. When most photoconductors are used in photoconductivecompositions, the surface potentials of such resultant compositionsusually drop below 100 volts and thus,

a definite speed can be ascertained. However, these speeds are improvedwhen the photoconductors of this invention are employed.

The preferred a, a'-bis(aminobenzylidene )aryldiaceton itrilephotoconductors of the invention are characterized by the followingformula:

b. phenoxyethyl, naphthoxymethyl,

f. alkylaminoakyl e.g. methylaminopropyl,

methylaminoethyl, etc., and also including dialkylaminoalkyl e. g.diethylaminoethyl,

dimethylaminopropyl, propylaminooctyl, etc.,

g. arylaminoalkyl, e.g., phenylaminoalkyl, diphenylaminoalkyl,N-phenyl-N-ethylaminopentyl, N-phenyl-N- ethylaminohexyl,naphthylaminomethyl, etc.,

h. nitroalkyl, e.g., nitrobutyl, nitroethyl, nitropentyl, etc.,

i. cyanoalkyl, e.g., cyanopropyl, cyanobutyl, cyanoethyl,

etc.,

j. haloalkyl, e.g., chloromethyl, bromopentyl, chlorooctyl,

etc.,

k. alkyl substituted with an acyl group having the formula wherein R ishydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, etc., lower alkylhaving one to eight carbon atoms e.g., methyl, ethyl, propyl, etc.,amino including substituted amino, e.g., diloweralkylamino, lower alkoxyhaving one to eight carbon atoms e.g., butoxy, methoxy, etc., aryloxy,e.g., phenoxy, naphthoxy, etc.; 4

. 2. an aryl group, e.g., phenyl, naphthyl, anthryl, fluorenyl, etc.,including a substituted aryl group such as a. alkoxyaryl, e.g.,ethoxyphenyl, methoxyphenyl, propoxynaphthyl, etc.,

b. aryloxyaryl, e.g., phenoxyphenyl, naphthoxyphenyl,

phenoxynaphthyl, etc.

c. aminoaryl, e.g., aminoanthryl, etc.,

d. hydroxyaryl, e.g., hydroxyphenyl, hydroxynaphthyl,

hydroxyanthryl, etc.,

e. biphenylyl,

f. alkylaminoaryl, e.g., methylaminophenyl,

methylaminonaphthyl, etc. and also including dialkylaminoaryl, e.g.,diethylaminophenyl, dipropylaminophenyl, etc.,

g. arylaminoaryl, e.g., phenylaminophenyl, diphenylaminophenyl,N-phenyl-N-ethylaminophenyl, naphthylaminophenyl, etc.,

h. nitroaryl e.g., nitrophenyl, nitronaphthyl, nitroanthryl,

aminophenyl, aminonaphthyl,

etc.,

i. cyanoaryl, e.g., cyanophenyl, cyanonaphthyl,

cyanoanthryl, etc.,

j. haloaryl, e.g., chlorophenyl, bromophenyl,

chloronaphthyl, etc., k. aryl substituted with an acyl group having theformula wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl,etc., amino including substituted amino, e.g., diloweralkylamino, loweralkoxy having one to eight carbon atoms, e.g., butoxy, methoxy, etc.,aryloxy, e.g., phenoxy, naphthoxy, etc., lower alkyl having one to eightcarbon atoms, e.g., methyl, ethyl, propyl, butyl, etc.,

1. alkaryl, e.g., tolyl, ethylphenyl, propyl, naphthyl, etc.;

R and R each represent any of the substituents set forth above for R R Rand R above and also can be hydrogen;

R R and R each represent any of the substituents set forth above for R,and R and also can be any of the following:

1. an alkoxy group having one to 18 carbon atoms, e.g., methoxy, ethoxy,propoxy, butoxy, etc.;

2. an aryloxy group e.g., phenoxy, naphthoxy, etc.;

3. halogen such as chlorine, bromine, fluorine or iodine.

Typical compounds which belong to the herein described general class ofphotoconductive materials include the following listed Table I below.

TABLE] I. a,a-Bis( p-diphenylaminobenzylidene )p benzenediacetonitrileII. a,a'-Bis( p-diphenylaminobenzylidene )obenzenediacetonitrile III.a,a Bis(p-diphenylaminobenzylidene )mbenzenediacetonitrile IV. a,a-Bis(p-diethylaminobenzylidene )pbenzenediacetonitrilea,a'-Bis(p-diethylaminobenzylidene)obenzenediacetonitrile VI.a,a'-Bis(p-diethylaminobenzylidene)mbenzenediacetonitrile VII. a,a'-Bis(p-diphenylamino-a-methylbenzylidene )-pbenzenediacetonitrile VIII.a,a-Bis(p-diphenylamino-a-phenylbenzylidene)-pbenzenediacetonitrile IX.01,01-Bis(4-diphenylamino-B-methylbenzylidene )-pbenzenediacetonitrileX. a,a'-Bis(4-diphenylamino-3-phenylbenzylidene)-pbenzenediacetonitrileXI.a,a'-Bis(4-diphenylamino-3-methoxybenzylidene)-pbenzenediacetonitrileXII.a,a-Bis(4-diphenylamino-B-phenoxybenzylidene)-pbenzenediacetonitrileXIII. a,a-Bis(4diphenylamino-3-chlorobenzylidene)-pbenzenediacetonitrileI XIV. oz,a-Bis(4-diphenylaminobenzylidene )-ptoluenediacetonitrile XV.a,a-Bis(4-diphenylaminobenzylidene )-panisolediacetonitrile XVI.01,01-Bis(4-diphenylaminobenzylidene)-p-(phenoxybenzene)diacetonitrileXVII.a,a'-Bis(4-diphenylaminobenzylidene)-p-(phenylbenzene)diacetonitrileXVIII. a,a'-Bis(4-diphenylaminobenzylidene )-p-(chlorobenzene)diacetonitrile Electrophotographic elements of theinvention can be prepared with the photoconducting compounds of theinvention in the usual manner, i.e., by blending a dispersion orsolution of a photoconductive compound together with a binder, whennecessary or desirable, and coating or forming a selfsupporting layerwith the photoconductor-containing materials. Mixtures of thephotoconductors described herein can be employed. Likewise, otherphotoconductors known in the art such as those described in Light,Belgian Pat. No. 705,117 dated Apr. 16, 1968 can be combined with thepresent photoconductors. In addition, supplemental materials useful forchanging the spectral sensitivity or electrophotosensitivity of theelement can be added to the composition of the element when it isdesirable to produce the characteristic effect of such materials.

The photoconductive layers of the invention can also be sensitized bythe addition of effective amounts of sensitizing compounds to exhibitimproved electrophotosensitivity. Sensitizing compounds useful with thephotoconductive compounds of the present invention can be selected froma wide variety of materials, including such materials as pyrylium dyesalts including thiapyrylium dye salts and selenapyrylium dye saltsdisclosed in VanAllan et'al. U.S. Pat. No. 3,250,615; fluorenes, such as7,12-dioxo-l 3-dibenzo (a,h)fluorene, 5,10- dioxo-4a,1l-diazobenzo(b)-fluorene, 3,13-dioxo-7-oxadibenzo (b,g)fluroene, and thelike; aggregate-type sensitizers of the type described in Light, BelgianPat. No. 705,117, dated Apr. 16, 1968; aromatic nitro compounds of thekinds described in U.S. Pat. No. 2,610,120; anthrones like thosedisclosed in U.S. Pat. No. 2,670,284; quinones, U.S. Pat. No. 2,670,286;benzophenones U.S. Pat. No. 2,670,287; thiazoles U.S. Pat. No.2,732,301; mineral acids; carboxylic acids, such as maleic acid,dichloroacetic acid, trichloroacetic acid and salicyclic acid; sulfonicand phosphoric acids; and various dyes, such as cyanine (includingcarbocyanine), merocyanine, diarylmethane, thiazine, azine, oxazine,xanthene, phthalein, acridine, azo, anthraquinone dyes and the like andmixtures thereof. The sensitizers preferred for use with the compoundsof this invention are selected from pyrylium salts includingselenapyrylium salts and thiapyrylium salts, and cyanine dyes includingcarbocyanine dyes.

Where a sensitizing compound is employed with the binder and organicphotoconductor to form a sensitized electrophotographic element, it isthe normal practice to mix a suitable amount of the sensitizing compoundwith the coating composition so that, after thorough mixing, thesensitizing compound is uniformly distributed in the coated layer.

Other methods of incorporating the sensitizer or the effect of thesensitizer may, however, be employed consistent with the practice ofthis invention. In preparing the photoconductive layers, no sensitizingcompound is required to give photoconductivity in the layers whichcontain the photoconducting substances, therefore, no sensitizer isrequired in a particular photoconductive layer. However, sincerelatively minor amounts of sensitizing compound give substantialimprovement in speed in such layers, the sensitizer is preferred. Theamount of sensitizer than can be added to a photoconductor-incorporatinglayer to give effective increases in speed can vary widely. The optimumconcentration in any given case will vary with the specificphotoconductor and sensitizing compound used. In general, substantialspeed gains can be obtained where an appropriate sensitizer is added ina concentration range from about 0.0,001 to about 30 percent by weightbased on the weight of the film-forming coating composition. Normally, asensitizer is added to the coating composition in an amount by weightfrom about 0.005 to about 5.0 percent by weight of the total coatingcomposition.

Preferred binders for use in preparing the present photoconductivelayers are film-forming, hydrophobic polymeric binders having fairlyhigh dielectric strength which are good electrically insulatingfilm-forming vehicles.

Typical ofthese materials are:

I. Natural resins including gelatin, cellulose ester derivatives such asalkyl esters of carboxylated cellulose, hydroxy ethyl cellulose, carboxymethyl cellulose, carboxy methyl hydroxy ethyl cellulose, etc.;

II. Vinyl resins including a. polyvinyl esters such as a vinyl acetateresin, a copolymer of vinyl acetate and crotonic acid, a copolymer ofvinyl acetate with an ester of vinyl alcohol and a higher aliphaticcarboxylic acid such as lauric acid or stearic acid, polyvinyl stearate,a copolymer of vinyl acetate and maleic acid, a poly(vinylhaloarylate)such as poly(vinylm-bromobenzoate-covinyl acetate), 2 terpolymer ofvinyl butyral with vinyl alcohol and vinyl acetate, etc.;

b. vinyl chloride and vinylidene chloride polymers such as apoly(vinylchloride), a copolymer of vinyl chloride and vinyl isobutylether, a copolymer of vinylidene chloride and acrylonitrile, aterpolymer of vinyl chloride, vinyl acetate and vinyl alcohol,poly(vinylidene chloride) a terpolymer of vinyl chloride, vinyl acetateand maleic anhydride, a copolymer of vinyl chloride and vinyl acetate,etc.;

styrene polymers such as polystyrene, a nitrated polystyrene, acopolymer of styrene and monoisobutyl maleate, a copolymer of styrenewith methacrylic acid, a

copolymer of styrene and butadiene, a copolymer of dimethylitaconate andstyrene, polymethylstyrene, etc.;

d. methacrylic acid ester polymers such as a poly(alkylmethacrylate),etc.;

e. polyolefins such as chlorinated polyethylene, chlorinatedpolypropylene, poly(isobutylene), etc.;

f. poly(vinyl acetals) such as poly(vinyl butyral), etc.; and

g. poly(vinyl alcohol);

III. Polycondensates including a. a polyester of 1,3-disulfobenzene and2,2-bis(4-hydroxyphenyl)propane;

b. a polyester of diphenyl-p,p-disulphonic acid and 2,2-

bis(4-hydroxyphenyl)propane;

c. a polyester of 4,4'-dicarboxyphenyl ether and 2,2-bis(4-hydroxyphenyl)propane;

d. a polyester of 2,2-bis(4-hydroxyphenyl)propane and fumaric acid;

e. polyester of pentaerythritol and phthalic acid;

f. resinous terpene polybasic acid;

g. a polyester of phosphoric acid and hydroquinone;

h. polyphosphites;

i. polyester ofneopentylglycol and isophthalic acid;

j. polycarbonates including polythiocarbonates such as the polycarbonateof 2,2-bis( 4-hydroxyphenyl)propane;

k. polyester of isophthalic acid,2,2-bis[4-(,B-hydroxyethoxy)phenyl]propane and ethylene glycol;

l. polyester of terephthalic acid,2,2-bis[4-(fi-hydroxyethoxy)phenyl]propane and ethylene glycol;

m. polyester of ethylene glycol, neopentyl,

terephthalic acid and isophthalic acid;

n. polyamides;

o. ketone resins; and

p. phenol-formaldehyde resins:

IV. Silicone resins;

V. Alkyd resins including styrene-alkyd resins, siliconealkyd resins,soya-alkyd resins, etc.;

VI. Polyamides.

VII. Paraffin; and

VIII. Mineral waxes.

Solvents useful for preparing coating compositions with thephotoconductor of the present invention can include a wide variety oforganic solvents for the components of the coating composition.

Typical solvents include:

I. aromatic hydrocarbons such as benzene, naphthalene, etc., includingsubstituted aromatic hydrocarbons such as toluene, xylene, mesitylene,etc;

2. ketones such as acetone, 2-butanone, etc.;

3. halogenated aliphatic hydrocarbons such as methylene chloride,chloroform, ethylene chloride, etc.;

4. ethers including cyclic ethers such as tetrahydrofuran, ethylether;

5. mixtures of the above.

In preparing the coating compositions utilizing the photoconductingcompounds disclosed herein useful results are obtained where thephotoconductive substance is present in an amount equal to at leastabout 1 weight percent of the coating composition. The upper limit inthe amount of photoconductive material present can be widely varied inaccordance with usual practice. It is normally required that thephotoconductive material be present in an amount ranging from about 1weight percent of the coating composition to about 99 weight percent ofthe coating composition. A preferred weight range for thephotoconductive material in the coating composition is from about 10weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support canvary widely. Normally, a wet coating thickness in the range of about0.001 inch to about 0.01 inch is useful in the practice of theinvention. A preferred range of coating thickness is from about 0.002inch to about 0.006 inch before drying although such thicknesses canvary widely depending on the particular application desired for theelectrophotographic element.

Suitable supporting materials for the photoconductive layers of thepresent invention can include any of the electrically conductingsupports, for example, various conducting papers; aluminum-paperlaminates; metal foils, such as aluminum foil, zinc foil, etc.; metalplates such as aluminum, copper, zinc, brass, and galvanized plates;vapor deposited metal layers such as silver, nickel or aluminum onconventional film supports such as cellulose acetate, poly(ethyleneterephthalate), polystyrene and the like conducting supports.

An especially useful conducting support can be prepared by coating atransparent film support material such as poly(ethylene terephthalate)with a layer containing a semiconductor dispersed in a resin. A suitableconducting coating can be prepared from the sodium salt of acarboxyester lactone of a maleic anhydride-vinyl acetate copolymer,cuprous iodide and the like, Such conducting layers and methods fortheir optimum preparation and use are disclosed in US. Pat. Nos.3,007,901, 3,245,833 and 3,267,807.

The compositions of the present invention can be employed inphotoconductive elements useful in any of the well knownelectrophotographic processes which require photoconducglycol,

tive layers. One such process is the xerographic process. in a processof this type, an electrophotographic element held in the dark, is givena blanket positive or negative electrostatic charge as desired byplacing it under a corona discharge to give a uniform charge to thesurface of the photoconductive layer. This charge is retained by thelayer owing to the substantial dark insulating property of the layer,i.e., the low conductivity of the layer in the dark. The electrostaticcharge formed on the surface of the photoconductive layer is thenselectively dissipated from the surface of the layer by imagewiseexposure to light by means of a conventional exposure operation such asfor example, by a contact-printing technique, or by lens projection ofan image, or reflex or bireflex techniques and the like, to thereby forma latent electrostatic image in the photoconductive layer. Exposing thesurface in this manner forms a pattern of electrostatic charge by virtueof the fact that light energy striking the photoconductor causes theelectrostatic charge in the light struck areas to be conducted away fromthe surface in proportion to the illuminance on a particular area.

The charge pattern produced by exposure is then developed or transferredto another surface and developed there, i.e., either the charged oruncharged areas rendered visible, by treatment with a medium comprisingelectrostatically responsive particles having optical density. Thedeveloping electrostatically responsive particles can be in the form ofa dust, or powder and generally comprise a pigment in a resinous carriercalled a toner. A preferred method of applying such a toner to anelectrostatic image for solid area development is by the use of amagnetic brush. Methods of forming and using a magnetic brush tonerapplicator are described in the following U.S. Pat. Nos. 2,786,439;2,786,440; 2,786,441; 2,81 1,465; 2,874,063; 2,984,163; 3,040,704;3,117,884 and reissue Re 25,779. Liquid development of the latentelectrostatic image may also be used. In liquid development thedeveloping particles are carried to the image-bearing surface in anelectrically insulating liquid carrier. Methods of development of thistype are widely known and have been described in the patent literature,for example, U.S. Pat. No. 2,297,691 and in Australian Pat. No. 212,315.In dry developing processes the most widely used method of obtaining apermanent record is achieved by selecting a developing particle whichhas as one of its components a low-melting resin. Heating the powderimage then causes the resin to melt or fuse into or on the element. Thepowder is, therefore, caused to adhere permanently to the surface of thephotoconductive layer. In other cases, a transfer of the charge image orpowder image formed on the photoconductive layer can be made to a secondsupport such as paper which would then become the final print afterdeveloping and fusing or fusing respectively. Techniques of the typeindicated are well known in the art and have been described in a numberof U.S. and foreign patents, such as U.S. Pats. Nos. 2,297,691 and2,551,582, and in RCA Review," vol. (1954) pages 469-484.

The compositions of the present invention can be used inelectrophotographic elements having many structural variations. Forexample, the photoconductive composition can be coated in the form ofsingle layers or multiple layers on a suitable opaque or transparentconducting support. Likewise, the layers can be contiguous or spacedhaving layers of insulating material or other photoconductive materialbetween layers or overcoated or interposed between the photoconductivelayer or sensitizing layer and the conducting layer. It is also possibleto adjust the position of the support and the conducting layer byplacing a photoconductor layer over a support and coating the exposedface of the support or the exposed or overcoated face of thephotoconductor with a conducting layer. Configurations differing fromthose contained in the examples can be useful or even preferred for sameor different application for the electrophotographic element.

The following examples are included for a further understanding of thisinvention.

EXAMPLE 1 Several coating dopes containing the following materials areprepared:

Organic photoconductor 0.5 g. Polymeric binder 1.5 g. Sensitizer 0.02 g.Methylene chloride 1 1.7 ml.

The resulting compositions are coated at a wet thickness of 0.004 inchon a conducting layer comprising the sodium salt of a carboxyesterlactone, such as described in U.S. Pat. No. 3,120,028, which in turn iscoated on a cellulose acetate film base. The coating blocks aremaintained at a temperature of F. These electrophotographic elements arecharged under a positive corona source until the surface potentials, asmeasured by an electrometer probe, reach between about 600 volts. Theyare then subjected to exposure from behind a stepped density gray scaleto a 3,000 K. tungsten source. The exposure causes reduction of thesurface potential of the portion of the element under each step of thegray scale from its initial potential, V0, to some lower potential, V,whose exact value depends on the actual amount of exposure inmeter-candle-second received by the area. The results of themeasurements are plotted on a graph of surface potential V vs. logexposure for each step. The speed is the numerical expression of 10multiplied by the reciprocal of the exposure in meter-candle-secondsrequired to reduce the 500 to 600 volt charged surface potential tovolts above 0 volt. The reduction of the surface potential to 100 voltsor below is significant in that it represents a requirement for suitablebroad area development ofa latent image. This speed at 100 volts is ameasure of the ability to produce and henceforth to develop or otherwiseutilize the charge image, higher speeds requiring less illumination toproduce a usable charge image. When the photoconductor is absent fromthe coating, the surface potential does not drop to, or below, 100 voltsand no speed value can be assigned. This is also the case when acompound is present in the composition but is ineffective as aphotoconductor. The speeds of the various photoconductive compositionsare shown in Table 11 below. The sensitizers used are referred to belowas follows:

B. 2,6-bis(4-ethylphenyl)-4-(4-amyloxyphenyl)thiapyryliurn perchlorateE. Rhodamine B F. 2,4-bis(4-ethoxyphenyl)-6-(4-n-amyloxystyryl)pyryliumfluoroborate H.2,6-bis(4-ethoxyphenyl)-4-(4-n-amyloxyphenyl)thiapyrylium perchlorateThe binders used are referred to below as follows:

Vitel a polyester resin sold by Goodyear Tire and Rubber Co. comprisingpoly(4,4-isopropylidenebisphenyleneoxyethylene-co-ethyleneterephthalate)Pvm BB poly(vinyl-m-bromobenzoate-co-vinylacetate) The photoconductorused is Compound I of Table I.

TABLE ll Sensitizer Binder Speed Vitel Vitel Pvm BB Pvm BB Vitel EXAMPLE2 related material. The speed data in the following Table IIIdemonstrates that the photoconductors of this invention aresubstantially faster than the photoconductor used in this Ex ample.

TABLE III Sunni/e1 Binder Speed Vitcl Vite] Pvm BB Pvm BB Vite] EXAMPLE3 A composition in the form of a dope consisting of the followingmaterials is coated at a wet thickness of0.004 inch on a poly(ethyleneterephthalate) film support bearing a conducting layer of sodium salt ofa carboxyester resin lactone:

Photoconduclor 025 g. Polymeric binder Vitel LOO g. Sensitizer 0.0] g.Dichloromelhane 9.60 g.

The coating block is maintained at a temperature of 90 F. until thesolvent is removed. In a darkened room, the surface of thephotoconductive layer so prepared is charged to a potential of about+600 volts under a corona charger. The layer is then covered with atransparent sheet bearing a pattern of opaque and light-transmittingareas and exposed to the radiation from an incandescent lamp with anillumination intensity of about 75 meter-candles for 12 seconds. Theresulting electrostatic latent image is developed by cascading over thesurface of the layer negatively charged black thermoplastic tonerparticles on glass bead carriers. The quality of the images reproducedusing the various photoconductors described herein are set forth in thefollowing Table V.

TABLE V Photoconductor Image Quality none non reproduced I Good II GoodIII Good IV Good V V Good The invention has been described in detailwith particular reference to preferred embodiments thereof, but, it willbe understood that variations and modifications can be efiected withinthe spirit and scope of the invention.

I claim:

1. In an electrophotographic process for reproducing continuous toneimages wherein an electrostatic charge pattern is formed on anelectrophotographic element, the improvement characterized in that saidelectrophotographic element has a photoconductive layer comprising aphotoconductor having the formula:

wherein R R R and R are each selected from the group consisting of anaryl group and an alkyl group,

R and R are each selected from the group consisting of an alkyl group,an aryl group and a hydrogen atom and R R and R are each selected fromthe group consisting of an alkyl group, an aryl group, an alkoxy group,an aryloxy group, a halogen atom and a hydrogen atom.

2. The process of claim 1 wherein R R R and R are aryl groups.

3. The process of claim 1 wherein R R and R are hydrogen atoms.

4. The process of claim 1 wherein R and R are hydrogen atoms.

5. The process of claim I wherein said photoconductive compositioncontains a sensitizer for said photoconductor.

6. In an electrophotographic process for reproducing continuous toneimages wherein an electrostatic charge pattern is formed on anelectrophotographic element, the improvement characterized in that saidelectrophotographic element has a layer of a photoconductive compositioncomprising:

a. from about 10 to about 60 percent by weight based on saidphotoconductive composition of a, a'-bis(p-diphenylaminobenzylidene)-p-bezenediacetonitrile as the organicphotoconductor,

b. a film-forming polymeric binder for said photoconductor and c. fromabout 0.005 percent to about 5 percent by weight based on saidphotoconductive composition of a sensitizer for said photoconductivecomposition.

2. The process of claim 1 wherein R1, R2, R3 and R4 are aryl groups. 3.The process of claim 1 wherein R7, R8 and R9 are hydrogen atoms.
 4. Theprocess of claim 1 wherein R5 and R6 are hydrogen atoms.
 5. The processof claim 1 wherein said photoconductive composition contains asensitizer for said photoconductor.
 6. In an electrophotographic processfor reproducing continuous tone images wherein an electrostatic chargepattern is formed on an electrophotographic element, the improvementcharacterized in that said electrophotographic element has a layer of aphotoconductive composition comprising: a. from about 10 to about 60percent by weight based on said photoconductive composition of Alpha ,Alpha ''-bis(p-diphenylaminobenzylidene)-p-bezenediacetonitrile as theorganic photoconductor, b. a film-forming polymeric binder for saidphotoconductor and c. from about 0.005 percent to aBout 5 percent byweight based on said photoconductive composition of a sensitizer forsaid photoconductive composition.